machine/rp2040: implement UART0/UART1, can be used on all rp2040 boards

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/machine/machine_rp2040.go

@@ -4,7 +4,7 @@ package machine
 
 import (
 	"device/rp"
-	_ "unsafe"
+	"runtime/interrupt"
 )
 
 const (
@@ -82,3 +82,35 @@ func machineInit() {
 func ticks() uint64 {
 	return timer.timeElapsed()
 }
+
+// UART pins
+const (
+	UART_TX_PIN  = UART0_TX_PIN
+	UART_RX_PIN  = UART0_RX_PIN
+	UART0_TX_PIN = GPIO0
+	UART0_RX_PIN = GPIO1
+	UART1_TX_PIN = GPIO8
+	UART1_RX_PIN = GPIO9
+)
+
+// UART on the RP2040
+var (
+	UART0  = &_UART0
+	_UART0 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    rp.UART0,
+	}
+
+	UART1  = &_UART1
+	_UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    rp.UART1,
+	}
+)
+
+var Serial = UART0
+
+func init() {
+	UART0.Interrupt = interrupt.New(rp.IRQ_UART0_IRQ, _UART0.handleInterrupt)
+	UART1.Interrupt = interrupt.New(rp.IRQ_UART1_IRQ, _UART1.handleInterrupt)
+}